1. Field of the Invention
The present invention relates to syringes and needles and more particularly concerns disposable syringes and needles having re-use prevention and medication saving features.
2. Background
Throughout the world the multiple use of hypodermic syringe products, which are intended for single use only, is instrumental in drug abuse and in the transfer of contagious diseases. Intravenous drug users who routinely share and re-use syringes are a high risk group with respect to the AIDS virus. Also, the effects of multiple use are a major concern in some countries where repeated use of syringe products during mass immunization programs may be responsible for the spread of many diseases. Re-use of single use hypodermic syringe assemblies is also instrumental in the spread of drug abuse even in the absence of infection or disease.
Many attempts have been made to remedy this problem. Most notable are early contributions which relied on a specific act to destroy the syringe after use either by using a destructive device or providing a syringe assembly with frangible zones so that the syringe could be rendered inoperable by the application of force. Other attempts involve the inclusion of structure which would allow the destruction or defeating of the syringe function through a conscious act by the syringe user. Although many of these devices work quite well they do require the specific intent of the user followed by the actual act to destroy or render the syringe inoperable. These devices are not effective with a user having the specific intent to re-use the hypodermic syringe. Accordingly, there is a need for a single use hypodermic syringe which becomes inoperative or incapable of further use automatically without any additional act on the part of the user. This automatic function is much harder to provide because the means for rendering the syringe inoperable must not prevent its filling or use under normal conditions.
In single-use syringes using needle assemblies having a hub attached to a needle cannula there is a need to help prevent reuse of the needle assembly after its use with the single-use syringe so that the needle assembly cannot be used again with other syringes or fluid handling devices.
There is also a need in single-use syringes to minimize or eliminate wasted medication in the injection process. This is especially true in mass inoculation programs involving large numbers of people and in many cases limited financial resources. Medication which is not delivered, because it is trapped in the interior of the syringe tip after the plunger reaches its maximum distal displacement, can prove costly. Even with a small number of injections, an entire dose may be lost through medication which is trapped in the syringes and not delivered.
n operable syringe assembly includes a barrel having an inside surface describing a chamber for retaining fluid. The barrel includes an open proximal end, a distal end and an elongated tip extending from the distal end having a passageway therethrough in fluid communication with the chamber. The tip has a side wall tapered proximally outwardly at a taper of from 4% to 8%. A plunger rod includes an elongated body portion having a proximal end, a distal end and a stopper at the distal end. The stopper is slidably positioned in fluid-tight engagement in the barrel. An elongated projection extends distally outwardly from the distal end of the plunger rod and is shaped to fit within the passageway of the elongated tip of the barrel. Structure for preventing proximal motion of the plunger rod with respect to the barrel after distal motion of the stopper to expel fluid through the passageway is provided. A needle assembly includes a cannula having a proximal end, a distal end and a lumen therethrough and a hub having an open proximal end with a tapered cavity therein including a side wall tapered distally inwardly at a taper of about 4% to 8%. The cavity has a diameter of less than about 3.85 mm at the open proximal end. The hub includes a distal end joined to the proximal end of the cannula so that the lumen is in fluid communication with the cavity. A needle shield is removably connected to the hub so that the distal end of the cannula is in the needle shield. A package encloses the syringe assembly and the needle assembly.
In other embodiments the side wall of the tip has a taper of about 6% and the side wall of the hub has a taper of about 6%.
Another embodiment of the present invention includes a needle assembly with a cannula having a proximal end, a distal end, and a lumen therethrough and a hub having an open proximal end with a tapered cavity therein. The tapered cavity has a side wall tapered distally inwardly at a taper of from 4% to 8%, preferably 6%, and a diameter of less than about 3.85 mm at its open proximal end. The hub includes a distal end joined to the proximal end of the cannula so that the lumen is in fluid communication with the cavity.